The present invention relates to a process for manufacturing multi-layer composites with sensitive outer surfaces and to a process for protecting sensititive outer surfaces from mechanical and physical effects, in particular the effects of pressure and/or heat, whereby the sensititive surfaces are covered by a protective layer during the application of pressure and heat.
Known, for example from EP 0 423 074, is the manufacture of multi-layer composites having a core layer of thermoplastic material with an outer layer of metal on both sides. The core layer and the outer layers are joined together permanently in a continuous process under pressure between two rolls at elevated temperature. The composite can be coated with a protective film.
The protective film, which is intended to protect the final product until its final stage of processing, can advantageously be deposited on the outer surface of the composite in a single lamination process. During the processing of the layers into a composite, the surfaces of the, possibly lacquered, polymer-coated, or otherwise treated, outer layers of plastic or metal are exposed to demanding conditions resulting from the effects of pressure and heat. Protective films are not capable of protecting the surface from harmful effects at all times. Discoloration of the surface can result, or the surface can be damaged as a result of mechanical effects.
The object of the present invention is to propose a process which enables optimal joining of the individual layers to be achieved under free choice of the parameters of heat and presssure without detriment to the outer surfaces of the outer layers.